Speaking to supporters in Auckland, Prime Minister Bill English underscored that "just short of half of all New Zealanders voted National" but said it was clear his party could not form government alone.

Under New Zealand's proportional voting system, large parties typically must form alliances with smaller ones in order to govern.

"As we go into negotiations with the intention of forming a stable government that enables this country to deliver for New Zealanders," Mr English said.

"In the next few days we will begin discussions with New Zealand First, finding common ground, and, most importantly, taking on the responsibility of forming the kind of government that will enable New Zealand to get on with its success."

"We don't need to rush this process."

That means there is still a chance Mr English's main challenger, Labour's Jacinda Ardern, could get the top job.

"I simply cannot predict at this point what decisions other leaders will make."

Ms Ardern said it would be difficult to complete coalition talks before all votes were tallied.

Speaking outside her home in Auckland on Sunday (local time), Ms Ardern told media that her centre-left party would not concede, despite lagging almost 10 points behind the incumbent National Party, which received 46 per cent of the vote.

Votes for the Green Party, which has a working agreement with Labour, reached 5.8 per cent.

Ms Ardern, the 37-year-old who only became Opposition Leader in August and dramatically improved Labour's position in opinion polls, was vying to become New Zealand's third female prime minister and the youngest in modern history.

She said she was "humbled by this election" and thanked volunteers for their help.

"On this night I pledge all my energies, my every waking moment to ensure that no matter where tonight's result takes us, I am committed to a future we can all be proud of, a future that is better," she said.

New Zealand First leader Winston Peters, who has been branded the election king or queenmaker by the NZ press, said on Sunday (local time) he had begun talks with members of his nationalist party about who to support in a coalition government, but declined to put a timeframe on a decision.

Mr Peters is in a position of power after Saturday's vote, with the ruling National Party and the opposition Labour Party needing his party's support to form a government under the nation's proportional representation system.

"I'm doing it one-by-one by phone," New Zealand First leader Winston Peters told reporters, adding that he had not received any calls from the National Party or the Labour Party about coalition talks and has not contacted them.

Asked by a reporter about how long he expected a decision to take, Mr Peters replied: "How long before I pick you up and throw you into the water over there?"

He noted that in some countries forming a government after a close election has taken months.

Moscow's words and actions — including the alleged poisoning of a former spy — are not the results of random aggression but rather fall into distinct patterns that can help us anticipate Russia's next moves under Vladimir Putin.